One type of electrostatographic reproducing machine is a xerographic copier or printer. In a typical xerographic copier or printer, a photoreceptor surface, for example that of a drum, is generally arranged to move in an endless path through various processing stations of the xerographic process. As in most xerographic machines, a light image of an original document is projected or scanned onto a uniformly charged surface of a photoreceptor to form an electrostatic latent image thereon. Thereafter, the latent image is developed with an oppositely charged powdered developing material called toner to form a toner image corresponding to the latent image on the photoreceptor surface. When the photoreceptor surface is reusable, the toner image is then electrostatically transferred to a recording medium, such as a sheet of paper, and the surface of the photoreceptor is cleaned and prepared to be used once again for the reproduction of a copy of an original. The sheet of paper with the powdered toner thereon in image-wise configuration is separated from the photoreceptor and moved through a fusing apparatus including a heated fusing member and a pressure member forming a fusing nip through which the toner image on the sheet of paper is heated and permanently fixed or fused to the sheet of paper. Typically the fusing apparatus is a roller type apparatus in which the heated fusing member and the pressure member are rollers.
Because copy sheets come in different lengths, fusing apparatus rollers are usually longer longitudinally than most copy sheet lengths. One problem typically encountered in such fusing apparatus when fusing copy sheets shorter (longitudinally) than the fusing rollers is the problem of copy sheet edge wear on the rollers, particularly on the fuser roller. Copy sheet edge wear is premature wear and occurs on the fuser roll and/or pressure roller at where the copy sheet edges are on the inboard and outboard ends of the rollers. The problem as such typically creates undesirable and unscheduled fuser roll and/or pressure roller maintenance/replacement before the fuser module as a whole has reached its end of life. This problem has been around for years, many solutions have been suggested but currently no one effective solution exists.
Prior art that may be relevant in considering the present disclosure for example include what is taught in the following references. U.S. Pat. No. 5,253,026 issued Oct. 12, 1993 to Tamary and entitled “Fusing apparatus having variable shape fuser roller” discloses a fusing apparatus for fusing toner images onto a substrate. The fusing apparatus has a generally cylindrical pressure roller, a fuser roller, and a device for applying toner release oil to the surface there of. The fuser roller further includes a first length portion that has a generally cylindrical outer shape for contacting the pressure roller to form a fusing nip through which the substrate can be moved. In order to prevent damage to the surface of the fuser roller, the fuser roller includes a second length portion which lies towards an end of the fuser roller away from the fusing nip and has a generally conical outer shape for preventing contact between the fuser roller and pressure roller.
U.S. Pat. No. 5,130,754 issued Jul. 14, 1992 to Hishikawa and entitled “Conveying rotatable member and conveying apparatus” discloses an image forming apparatus with an image forming device for forming an unfixed image on a recording material and; first and second rotatable members for forming a nip for conveying the recording material supporting the unfixed image. The second rotatable member has its maximum diameters between a longitudinal center and one longitudinal end and between the center and the other longitudinal end thereof.
U.S. Pat. No. 4,594,068 issued Jun. 10, 1986 to Bardutzky et al. and entitled “Roll-fusing apparatus” discloses a roll-fusing apparatus comprising a heated fusing roller and a pressure roller which form a roller gap therebetween. The shape of the non-cylindrical roller core and the coating of the pressure roller makes it possible to fuse the toner images on copy supports which remain free of wrinkles after passing through the roller gap. In addition, duplication of the copy image does not occur up to DIN A1 size copies. The roller core and the coating of the pressure roller, comprising a silicone elastomer coating and a shrunk-on tubing have varying thicknesses over the length of the roller. As a result, the speed of passage of the copy support at the edges of the roller gap is modified, compared with the speed of passage obtained with a pressure roller having a cylindrical roller core and a cylindrical coating.
U.S. Pat. No. 4,253,392 issued Mar. 3, 1981 to Brandon et al. and entitled “Hollow fuser roll with variable taper” discloses an electrophotographic copier machine with a roll fuser where one of the mating rolls is comprised of a thin outer shell which takes a variable taper so that a concave shape is produced under high humidity conditions and a relatively straight roller is produced under low humidity conditions. Means for changing the support at the roll ends is provided to produce the variable taper. End plugs can be moved axially inward at high humidity to provide support for the end portions of the normally concave roll and can be moved axially outwardly under low humidity such that no support is provided until the roll ends are flattened under the pressure of a mating roll.
U.S. Pat. No. 6,969,021 issued Nov. 29, 2005 to Nibarger and entitled “Variable curvature in tape guide rollers” discloses an apparatus is provided for reducing tape media edge damage in data regions and controlling the position of the tape media in a passive manner. A curved tape guide surface of a tape guide roller controls tape media edge damage by restoring the tape media to a properly aligned position on a tape guide roller by using tape guide rollers with curved edge stops that exert a force to the tape media during a lateral shift. As the tape moves around the roller, the restoring force exerted by the curved portion of the tape guide roller on the tape during any lateral shift restores the tape to a centered position. Keeping the tape media in a centered position reduces tape edge wear, lessens degradation of the integrity of the tape and increases the useful lifetime of the tape.
U.S. Pat. No. 5,490,029 issued Feb. 6, 1996 to Madsen et al. and entitled “Compliant tape guide for data cartridges” discloses a compliant tape guide for magnetic tape transported in a belt driven data cartridge which resiliently engages one edge of a tape and urges the tape to a position against a fixed flange. The compliant tape guide includes a spring strip having a flange end and a spring finger to load the flange end against the tape. The compliant guide reduces tape edge wear as well as providing for better tracking of the tape.